Abdomen Adult Mosquito

The abdomen consists of 10 segments of which only eight are distinctly visible. Segments IX and X are reduced and more or less modified as part of the external structures involved in reproduction, the genitalia. In some species segment VIII is sexually differentiated from the preceding segments, and in such cases it is also treated as part of the genitalia. Each segment consists of a dorsal sclerite, the tergum (pl. terga), which is joined by an elastic pleural membrane to a ventral sclerite, the sternum (pl. sterna). Intersegmental membrane connects the terga and sterna of adjacent segments. It is the elasticity of the pleural and intersegmental membranes that allows the abdomen of the female mosquito to become distended when she is taking a blood meal or when she is gravid and full of eggs. The terga are collectively referred to as the dorsum; likewise the sterna as the venter. Both the dorsum and venter are clothed with scales in culicines and toxorhynchitines, but are usually bare or have few scales in anophelines. The terga may have basal, apical or lateral patches of pale scales which provide useful taxonomic characters. Scale patterns are generally not so evident on the sterna.

The male genitalia of mosquitoes (segments VIII-X) undergo a clockwise or counter clockwise rotation of 180° shortly after emergence which results in a reversal of the dorsal and ventral structures. To avoid confusion, these structures are referred to in their original positions before rotation (dorsal and ventral, or tergal and sternal) even thought they appear to occupy the opposite positions in the mature specimen. Modifications of the genital parts are more or less complex and varied according to the genera and species, thus providing important taxonomic characters. Female genitalia have been largely neglected in mosquito taxonomy, but certain prominent structures have been used to a limited degree in recognising species of certain genera.